In the United States, it has been considered advisable to position infants, herein referring to as newborn babies up to the age of one year, so that they will sleep on their stomachs, a prone position, to keep the infants from choking if they burp or spit-up while sleeping. The American Academy of Pediatrics has recently recommended to doctors that infants sleep supine, that is on their sides or backs, because of a link between an increased risk of Sudden Infant Death Syndrome (SIDS) and the prone position. SIDS is a mysterious affliction that strikes infants without warning and the infants suddenly stop breathing for reasons that is still not understood and that don't show up on autopsies. In a period of 1980 to 1987 in the United States, there was a male death rate of 0.16% from SIDS, with a female death rate somewhat less. While the syndrome can occur anytime during the first year of life, about 90% of the cases cluster in babies 2 to 6 months of age. SIDS strikes about 1 in every 1,000 infants in the United States and kills an estimated 6,000 babies yearly.